The present invention relates generally to tubes, and more particularly to a method for manufacturing a tubular assembly.
Resistance welding (also known as electric-resistance welding) is a known metallurgical process wherein metal is heated by its own resistance to a semi-fused (i.e., soft) or fused (i.e., molten) state by the passage of very heavy electric currents for very short lengths of time and then welded by the application of pressure.
Conventional methods for manufacturing a metallic tubular assembly include shaping the tubes, if and as required, to their desired shape for the tubular assembly such as by bending or hydroforming. Then, expensive manipulating equipment is used to position the shaped tubes for conventional welding as the tubular assembly is being weld-assembled.
Conventional welding includes gas metal arc welding. Gas metal arc welding uses a consumable metal wire as one electrode and the parts as another electrode, and moves the consumable metal wire (or the parts) to draw an arc and weld the parts together. The welding is accompanied by a gas (such as a mixture of argon and carbon dioxide) to prevent oxidation and stabilize the arc. Such gas metal arc welding is well known. In a conventional gas metal arc welding technique, solid metal wire or metal core wire (i.e., an annular-solid wire whose core is filled with metal powder such as a mixture of metal, alloy and/or oxide powders) is used with the wire at a positive electrical welding potential and with the parts electrically grounded. The welding arc creates a molten weld puddle which results in the welding together of the parts. A ceramic ferrule is used to contain the weld puddle when needed. Gas metal arc welding requires expensive welding equipment, the molten weld puddle tends to flow away from the joint area resulting in welds of inconsistent quality, and the process requires a long cycle time between welds.
Conventional methods for attaching parts together also include friction welding. To join two tubes together end to end, one of the tubes is rotated about its longitudinal axis, and the tube ends are pressed together, wherein friction causes heating of the ends creating the weld. To join a tube to a plate, the tube is rotated about its longitudinal axis, and the tube end and the plate are pressed together, wherein friction causes heating, creating the weld. Friction welding requires expensive welding equipment, and the process requires a long cycle time between welds.
What is needed is a less expensive method for manufacturing a metallic tubular assembly.
A first method of the invention is for manufacturing a metallic tubular assembly and includes steps a) through f). Step a) includes obtaining a first tube. Step b) includes obtaining a first tubular connector having a first end portion and a second end portion. Step c) includes, after steps a) and b), metallurgically attaching the first end portion to the first tube. Step d) includes obtaining a tubular member having a third end portion, wherein at least one of the second and third end portions includes an outward fold, and wherein the fold includes spaced-apart first and second fold portions. Step e) includes, after steps a) through d), positioning the first tubular connector and the tubular member with the second end portion aligned with and contacting the third end portion. Step f) includes, after step e), creating a resistance welding current path through the first tubular connector and the tubular member proximate the second and third end portions and relatively and deformingly moving together the second and third end portions creating a weld zone which includes at least some of the second and third end portions.
A second method of the invention is for manufacturing a metallic tubular assembly and includes steps a) through g). Step a) includes obtaining a substantially-straight first tube. Step b) includes obtaining a first tubular connector having a first end portion and a second end portion. Step c) includes, after steps a) and b), annularly metallurgically attaching the first end portion to the first tube. Step d) includes, after step c), changing the shape of the first tube. Step e) includes obtaining a substantially-straight tubular member having a third end portion, wherein at least one of the second and third end portions includes an annular outward fold, and wherein the fold includes spaced-apart first and second fold portions. Step f) includes, after steps a) through e), positioning the first tubular connector and the tubular member with the second end portion aligned with and contacting the third end portion. Step g) includes, after step f), creating a resistance welding current path through the first tubular connector and the tubular member proximate the second and third end portions and relatively and deformingly moving together the second and third end portions creating an annular weld zone which includes at least some of the second and third end portions.
A third method of the invention is for manufacturing a metallic tubular assembly and includes steps a) through h). Step a) includes obtaining a first tube. Step b) includes obtaining a first tubular connector having a first end portion and a second end portion. Step c) includes, after steps a) and b), annularly metallurgically attaching the first end portion to the first tube. Step d) includes obtaining a second tube. Step e) includes obtaining a second tubular connector having a third end portion and a fourth end portion, wherein at least one of the second and third end portions includes an annular outward fold, and wherein the fold includes spaced-apart first and second fold portions. Step f) includes, after steps d) and e), annularly metallurgically attaching the fourth end portion to the second tube. Step g) includes; after steps a) through f), positioning the first tubular connector and the second tubular connector with the second end portion aligned with and contacting the third end portion. Step h) includes, after step g), creating a resistance welding current path through the first and second tubular connectors proximate the second and third end portions and relatively and deformingly moving together the second and third end portions creating an annular weld zone which includes at least some of the second and third end portions.
Several benefits and advantages are derived from one or more of the methods of the invention. Resistance welding is less expensive than gas metal arc welding or friction welding. Resistance welding also has a shorter cycle time between welds than gas metal arc welding or friction welding.